I would say the big one to start is Family Traditions, and the like. Ideas:

• A weekly or bi-weekly date night where you go do something different (no dinner-and-a-movie.)

• If you don't usually have a "Family Dinner", make one day of the week a "Family Dinner" night.

• Weekly or monthly get-together where you can hash out plans, see what's been problematic, hopefully correct things before they lead to arguments, etc

• The yearly traditions such as: having a jar where you write down all the awesome things that happened on slips of paper, and read the paper on New Years, various holiday traditions, or yearly vacations, or whatnot